The present technology relates to a semiconductor substrate provided with a thin-film transistor that includes an organic semiconductor layer, and to an electronic device using the same.
In recent years, various electronic devices use a thin-film transistor (TFT) as a switching element or others, and the TFT is mounted to the electronic devices as a part of a semiconductor substrate. As the TFT, an organic TFT using an organic semiconductor material for forming a semiconductor layer (channel layer) has been recently considered as a promising alternative to an inorganic TFT using an inorganic semiconductor material therefor. This is because, with the organic TFT, the semiconductor layer is able to be formed by coating so that the cost reduction is achieved. Also with the organic TFT, the semiconductor layer is able to be formed at a temperature lower than that for vapor deposition or others, thereby allowing the use of a low-heat-resistant flexible plastic film or others as a support base.
Among the electronic devices including the organic TFT, some such as a display device use a light source. Such a display device is typified by an organic electroluminescence (EL) display device including a light-emitting layer, a liquid crystal display device provided with a backlight, or others.
The concern here is that when light from the light source reaches the organic semiconductor layer of the organic TFT, the organic semiconductor layer may unexpectedly absorb the light of some wavelength range. This causes unpredictable doping in the organic semiconductor layer, and as a result, electrical characteristics such as threshold voltage easily deteriorate in the organic TFT.
For reducing the influence of light from the light source, several related technologies have been proposed so far. To be specific, in an organic EL display device using an inorganic TFT, in order to prevent deterioration in the electrical characteristics of an inorganic semiconductor layer made of amorphous silicon or others, a light-shielding layer in the color of black is provided between a light-emitting layer and the inorganic TFT (for example, see Japanese Unexamined Patent Application Publication No. 2002-108250). Moreover, in a liquid crystal display device using an organic TFT, in order to prevent the deterioration in the electrical characteristics of an organic semiconductor layer made of pentacene or others, a light-shielding film in use is a gate electrode provided between a backlight and the organic semiconductor layer (for example, see Japanese Unexamined Patent Application Publication No. 2006-114862).